ws2813 vs ws2815 - voltage/ amperage question.

  • Hello everyone!
    Total novice here. I have a programming background but no experience with electric circuits/soldering etc.
    My current setup/ idea is as follows:
    hdmi switch > hdmi splitter > hdmi capture > led strips connected to RP4b w 8Gb GPIO 18 > led strips powered by a cable with THIS connector to a power supply.
    I have decided to go with 60 led strip and has already selected the ws2813. By my calculations, I would need 5v 18amps to power 3.9 meters behind my tv. This also means I would need to buy it for ~$25-30.
    Then I have discovered ws2815, which uses 12V and doesn't have a voltage drop. By my calculations, it would need 12v 4amp power and I have 12v3am and 12v5amp power bricks laying around. The price is almost identical to buy 2813 + power supply or ws2815 + less e-waste.

    While doing research, I found 2 things that worry me. First, feedback on some of the power connectors say "do not overpower, 5amp max" and with ws2813 I would need to use 15amp (although the LED vendor sells power brick with the connector). Second, I read a comment that going 12v without soldering is dangerous and should be avoided.

    I would like some feedback on my current set up and thought process. Don't want to fry either LED strips or RasbPi.
    I can upgrade to use a breadboard or USB CONNECTOR to enable sound later on but for now, just would like to connect/ ground to Rasp Pi directly.

    Thank you in advance!

  • So many questions :LOL: tough call tho, making do with what you have may be cheaper but more expensive in the long run if its not got the power to do the job..

    Slightly confused by your electrical calculations they worry me :LOL:

    Regardless if you use 5v or 12v leds you will need to work out the max current that the entire strip can draw at max brightness (Current - in amps) and pick a power supply above that rating - for extra protection you can fuse the main supply to the leds so the strip cannot draw more than the max amount.

    You could use a 12v supply on a 5v strip but you'd need to drop the voltage down but the supply still needs to have the required Ampage to power the strips in the first place, you can also use the same supply to power the pi but you would need to add an extra 3amp on top of what the led strip requires so your other power supply's may not be up to the job.

    Once you have the correct power supply you can worry about the volt drops, each time you DO NOT use a soldered joint or add in a bad soldered joint or any sort of connector you run the risk of adding in points of failure, weak points or bad connections etc and that is what causes the actual volt drop in the circuit.

    Example would be a 40 strand wire - 39 strands are cut and only 1 remains intact, If you put a meter across that you may see next to no resistance but put a bulb at the other end and try to power it and its a different story - The current simply cant get to it fast enough to light it, same scenario with twisted wires, clip on connectors etc, it may not happen straight away but it's bad practice and can cause more problems later on as metal expands and contracts with heat so it could cause intermittent problems.

    So ideally solder any joints and add in additional power supply/earth connections to the strips to prevent volt drops across the circuit, regardless if they are 5v or 12v leds

    Don't use the pi as the only earth point for the leds, that's a accident waiting to happen, you need to earth the led strip back to the psu and tap into it for the earth on the pi GPIO

    Hope that helps you in someway, Good Luck

  • just make it easy on yourself and pick a 5 volts Ledstrip a.k.a APA102 or others that work normally without level shifters and arduino's.
    Normally with most ledstrips you can directly connect to the GPIO of the PI pins.

    in basics, the higher the voltage the lower the amps that is needed to accomplish the same power. P=UxI
    That said, go with a good clean steady 5 volts ( like a PSU of a pc) and use at least a PSU that is capable of delivering 10Amps for basics or more.

    simple calculation is; 30 leds/mtr use up half the current then 60 leds/mtr setups.
    A PI uses around 1 amps in fully operation, then u have 9 amps for the ledstrip and other stuff which is sufficient, although... PSU have to be a good build not some cheap powersource that isn't even putting out a decent DC.

    ground everything together and use more then one ground pin of the PI, also work with a multimeter that way you can measure the voltage/amps and contacts resistance. Ledstrips from certain types and PI's are really sensitive for either too much or too less of a DC's 5 volts.
    so with 5,20 volts it never works, and with 4.9 everything runs fine just for a example.

    goodluck with your build man.

    davieboy and me written at the same time a comment, so maybe there's double stuff in the comments.

  • Thank you guys! This was beyond informative.
    Ok, so I'm thinking I will go ws2801 / apa102 way with 30leds and if I want more light, I can order strips from Ali Express and wait.
    I was thinking to power the pi/ led strip independently.
    I'm going off of my co-worker setup + this video < link to the power connection timing.
    I do not have soldering tools or multimeter (and honestly already in the $200+ range in parts) and need things to be delivered before Christmas. Ugh.
    So for the 5v 30led strips, I was going to order THIS POWER SUPPLY. Would you say this is efficient or this is a "cheap power source"? And I guess I can go with 10amp vs 15amp for both?

    @jeroen warmerdam
    > ground everything together and use more then one ground pin
    > Don't use the pi as the only earth point for the leds, that's a accident waiting to happen, you need to earth the led strip back to the psu and tap into it for the earth on the pi GPIO

    Can I bother to clear this up? I was thinking of something like this:

    Where black and red connect to black and red on the DC Jack connector.
    Or like the guy did in the video. Maybe I lack the terminology when expressing myself.

    PS: Here's the list of things that I've got. Everything from RPI case down is purchased, choosing the Strips, L-shape solderless connectors and power supply based on the final decision.

    P.S.2 : Ugh, it seems my options (what's in stock) are: ws2801 or sk9822. (fake apa102)

  • OMG, you guys. /s
    So I'm currently going with sk9822 30 leds (going to get delivered by Christmas) + soldering kit + 4pin wire + power supply (thinking of switching to one of those metal PSUs, as they are half the price and I would have solder iron + multimeter).
    Wish me luck, haha.

  • the schematics/wiring is good, but use more GND pins ( just connect 3 GND pins together with a wire) and bring the GND back to ground of the PSU.
    in fact; bring all of your GND back to ground of your PSU, from all your devices.

    The pc PSU is really cheap, mostly you can strip them out of a old pc or buy them for 5 $.
    If you want to use them without a pc, you have to fire them up manually > bind 2 wires together ( mostly green and black right beside together in ATX connector)

    soldering the pins of the PI is 0% of resistance on the joints so thats a good way to go :)
    watch the arrow on the ledstrip/dataflow, it should be going away from your connection, also with lenghts of more then 2 meters of ledstrip then connect the begin and end of +5 and GND wires together>> so power them from both sides.

    good luck with your build and don't panic :)

  • lol yeah I thought you meant you were going to use the pi as the main earth point for it all, All i could think was poor lil pin.

    Remember and practise your soldering on numerous bits of wire before you touch the led strips, they can be quite intricate :thumbsup:

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